How valuable substances can be extracted from wood and plastic waste

In his doctoral project, Supriyanto has used a method of copyrolysis, which means that materials are heated in an oxygen-free environment to such high temperatures that the complex organic materials are broken down into valuable gases, liquids and solids and thus do not burn up.

Focus on gases

"In my project, I have particularly investigated the gases that are formed during the initial reactions during copyrolysis. By studying these early reactions, it was possible to determine both the composition and the amount of the gases that were formed," explained Supriyanto.

In particular, he examined the composition and quantity of the gases and concluded that this depends on the ratio of wood to plastic and the type of plastic used in co-pyrolysis. For example:

• Wood pyrolysis mainly produces oxygen-containing gases.
• Plastic pyrolysis mainly generates hydrocarbons.
• Co-pyrolysis of wood and plastic produces a mixture of both oxygenated gases and hydrocarbons.

"Some of the most exciting results were the effect of the ratio of wood to plastic. For example, if the wood content is 75 per cent, the formation of oxygen-containing gases is reduced by 90 per cent. If you instead add a catalyst, the total gas yield doubles," he said.

The gases released were separated, identified and quantified using advanced analytical techniques.

Significant practical applications

"Copyrolysis has a double advantage. By converting wood and plastic waste into valuable gases, it helps to reduce the amount of pollution and the gases that are formed can be used as renewable raw materials for the production of fuel and valuable chemicals, which promotes a circular economy and contributes to a more sustainable and environmentally friendly future," said Supriyanto.

Fills a knowledge gap

The doctoral project fills a knowledge gap and contributes to a deeper understanding of the mechanisms of gas formation during copyrolysis of wood and plastics, which can lead to the development of more efficient processes to convert waste into fuels and chemicals. 

The project is in line with several of the UN's Sustainable Development Goals (SDGs):

• SDG 7 (Affordable and clean energy): By producing renewable energy sources.
• SDG 12 (Responsible consumption and production): By recycling waste into resources.
• SDG 13: Climate action By reducing greenhouse gas emissions.

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Supriyanto completed his doctoral project at the Swedish Centre for Resource Recovery in the Sustainable Energy and Thermal Processes research group and defended his thesis on 21 March at the University of Borås.

Title of the thesis: Fast Co-pyrolysis of Wood and Plastic: Evaluation of Gases from Primary Reactions

Supervisor: Tobias Richards, professor

Assistant supervisor:
Anita Pettersson, Associate Professor
Päivi Ylitervo, Associate Professor

External reviewer: Leteng Lin, Associate Professor at the Department of Built Environment and Energy Technology, Linnaeus University

Read more about research in Resource Recovery and The Swedish Centre for Resource Recovery